For a number of years, there has been interest in achieving a tunable intense source of coherent radiation in the vicinity of 628 cm..sup.-1. This interest arises from a number of schemes which have been proposed to separate various isotopes of uranium in a multi-step process, one of whose steps requires radiation at approximately 628 cm..sup.-1. In this regard, see U.S. Pat. Nos. 3,443,087 and 3,937,956, as well as "Photochemical Isotope Separation as Applied to Uranium" (Union Carbide Corporation, Nuclear Division, Oak Ridge Gaseous Diffusion Plant, Mar. 15, 1972, K-L-3054, Revision 1, page 29) and "Some Developments in Laser Isotope Separation Research at Los Alamos" by Robinson and Jensen (A-UR-76-191) submitted to the American Physical Society meeting February 2-5, 1976, New York, New York.
The prior art is replete with techniques for producing intense coherent radiation at a variety of wavelengths, and further illustrates examples of apparatus that can be employed to tune such radiation to specific wavelengths. There are even examples of lasers which emit in the vicinity of 628 cm..sup.-1. For example, Lyon mentions, in U.S. Pat. No. 3,937,956, an HF laser emitting at 629.16 cm..sup.-1. For one reason or another the prior art techniques have not achieved what is required for the IR radiation step in the processes illustrated by the references cited above.
It is, therefore, one object of the present invention to provide apparatus emitting tunable intense coherent radiation at approximately 628 cm..sup.-1. It is another object of the present invention to provide such apparatus which is capable of being used in one or more of the isotope separation processes disclosed in present invention to provide such radiation by a classical laser which establishes a population inversion and produces stimulated emission as the population inversion is depleted. It is a further object of the present invention to produce such radiation by employing stimulated Raman scattering. It will be apparent from a reading of this description how the invention achieves these and other objects, which other objects will become apparent as this description proceeds.